Frozen Streams of Fowa Drift Border. — Wilson. 367 
anomalous topography. It is a narrow tongue of Niagara 
limestone, about a quarter of a mile long and but a few rod- 
wide, with nearly vertical walls rising about 100 feet above 
the water of the river, which Mows on three sides of it. Its 
narrow base and numerous deep fissures seem to render it im- 
possible that such a lofty and shattered wall, lying directly 
across the path of the glacier, at a point fully twelve miles 
from its nearest margin, could resist the force of the ice 
action. Yet glacial deposits are found on the summit of 
the Backbone. That these valleys and erosion forms are tin- 
work of the waters since the ice invasion, we cannot for a 
moment suppose. The explanation, then, of these anomalous 
and incongruous conditions, is the task undertaken in the 
present paper. As given beyond, this explanation was sug- 
gested by observations made in the spring of 1881 on a small 
tributary of the Little Turkey river, in the southeast corner 
of Clayton county, Iowa. 
The winter had been unusually long and severe. Snow 
covered the ground in October and increased at frequent in- 
tervals till the middle of the following March, when it lay 
over three feet in depth in the timber where not drifted. The 
temperature frequently fell below — 30°F. The steep hills 
that rise to a night of fully 500 feet on the east and west cut 
down the daylight in midwinter to little more than six hours 
in length. This small stream, which flows through the village 
of Jetfriesville, in a channel cut about live feet below the gen- 
eral level of the road, has its origin at the summit of the Ma- 
quoketa shales, at a point in the hills over 100 feet above the 
level of the village. 
This stream froze solid early in the winter. Then, as the 
warm water from the spring was constantly supplied, it soon 
sent a stream over its frozen bed. On the next cold night it 
froze solid again : and thus, by alternate flooding and freez- 
ing, re-enforced by the frequent snows, it had by the first of 
March filled its channel completely, had overspread it< banks 
with a belt of ice several rods in width and fully eight feet 
deep in places. It rose above the floors of the houses, and the 
residents made strenuous, and not always successful, efforts 
to keep the water out of their dwellings, by building walls of 
-now about the doors and cutting fresh channels for the 
stream. 
